RE: Clarification: Efficiency for detection of Tc-99m

["Moroney, Roger W" <Roger.Moroney@mkg.com>]

We had an intern prepare samples of our radiopharmaceuticals in various
geometry's and determine counting efficiencies for assorted detectors. For
Tc-99m and a Ludlum 44-9 pancake probe, we saw 0.35% at 1 inch (2.54 cm) and
0.53% at 1/2 inch (1.3 cm). This was for an aliquot deposited on a whatman
filter paper. The backing surface for the filter paper was a 1/2 inch thick
plexiglass sheet.

Not very good! We use the pancake for a gross personal contamination survey
just outside the Mo-99/Tc-99m generator production lab (actually all of our
labs) and then have our folks repeat with a NaI scintillation probe in a
lower background area. Then they walk through a portal monitor.

Roger Moroney
Health Physicist
Mallinckrodt, Inc.
314.654.7457 voice
314.654.7571 fax
roger.moroney@mkg.com


-----Original Message-----
From: Jacobus, John (OD) [mailto:JJacobus@exchange.nih.gov]
Sent: Friday, January 21, 2000 9:38 AM
To: Multiple recipients of list
Subject: Clarification: Efficiency for detection of Tc-99m


Please note that Tc-99m is used in nuclear medicine studies for in vivo
imaging.
It emits photons and conversion electrons.

Can anyone give me a reasonable detection efficiency for measuring Tc-99m
surface contamination using a GM pancake type probe?

-- John

John Jacobus, MS
Health Physicist
National Institutes of Health
Radiation Safety Branch, Building 21
21 Wilson Drive, MSC 6780
Bethesda, MD  20892-6780
Phone: 301-496-5774      Fax: 301-496-3544
jjacobus@exchange.nih.gov (W)
jenday@ix.netcom.com (H)
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